Electrically operated dust mask

ABSTRACT

A breathing filter for dust filtering masks in which electrodes in the form of insulated metal wires are employed. The polarity of the electrodes changes in periods which are of greater duration than the duration of dust particles in the filter, but is less than the time required for equalizing the difference in potential of the electrodes. Hardly any electrical energy is used so that a source of voltage of low yield can be used.

United States Patent 1 Walkenhorst [54] ELECTRICALLY OPERATED DUST MASK[75] Inventor: Wilhelm Walkenhorst, Bochum,

Germany [73] Assignee: Bergwerksverband GmbH, Essen- Kray, Germany 221Filed: Sept. 28, 1970 [21] Appl.No.: 76,033

[52] US. Cl. ..55/123, 55/131, 55/136, 55/146, 55/155, 55/485, 55/DIG.35 [51] Int. Cl ..B03c 3/04 [58] FieldofSearch....55/2,l55,123,131,132,143, 55/145,101,146,151,136,137, 485,DIG.

[56] References Cited UNITED STATES PATENTS 1,428,839 9/1922 Fortescue..55/151 X 2,067,822 l/l937 Biederman .....55/131 X 2,297,601 9/1942Williams ..55/132 2,381,455 8/1945 Jacob ..55/102 2,571,079 10/1951Warburton ..55/131 2,804,937 9/1957 .....55/103 2,814,355 11/1957.....55/132 12/1959 Powers ..55/132 C J O I I Q Q U I I I O Q I U 7 51Apr. 3, 1973 2,987,137 6/1961 Brixius et al ..55/138 3,304,251 2/1967Walker et al ..204/184 FOREIGN PATENTS OR APPLICATIONS 8,104 3/1933Australia ..55/101 183,768 8/1922 Great Britain ..55/136 717,705 11/1954Great Britain ..55/102 892,908 4/1962 Great Britain..... ....110/119215,135 11/1941 Switzerland ..55/137 1,040,379 10/1958 Germany ..55/131OTHER PUBLICATIONS German Printed Application No. 1,040,379, printed10-2-58, (3 sheet drawing 4 pages, spec.).

Primary ExaminerDennis E. Talbert, Jr. AttorneyMalcolm W. Fraser [57]ABSTRACT A breathing filter for dust filtering masks in which electrodesin the form of insulated metal wires are employed. The polarity of theelectrodes changes in periods which are of greater duration than theduration of dust particles in the filter, but is less than the timerequired for equalizing the difference in potential of the electrodes.Hardly any electrical energy is used so that a source of voltage of lowyield can be used.

2 Claims, 8 Drawing Figures PATENTEUAPH I973 3,724,17

sum 1 'UF 2 INVENTOR [0% ei/W 7 q wm aim PAHNI'EDAPM I975 SHEET 2 OF 2FIGZ INVENTOR MJM QJWM MMQM ELECTRICALLY OPERATED DUST MASK BACKGROUNDOF THE INVENTION The invention relates to a breathing filter for dustfiltering masks for the separation of particles out of gases through anon-homogeneous electric field, which is produced with the aid ofpositively and negatively charged electrodes.

Filters according to the invention are for removing dust, above allfinely divided dust, particularly out of the breathing air for theprevention of silicosis, whereby the temperature of the gases and theirmoisture should in principal remain without influence on the filteringeffect. These filters are particularly adapted for dust filtering masksin mining, in whose construction, the danger of explosion and otherconsiderations are additionally to be considered.

It is known that the dust carried away by gases, particularly by air,have electrical charges, which may derive from the comminution of thedust forming material, and frequently constitute several thousandelectric element charges. The polarity of the charges is different. Inmany cases, the charges are not distributed symmetrically, but outweighcharges of the one or the other indication. The electric separation ofdust rests on the forces which an electric field exerts on the charged,and under certain circumstances also on the uncharged particles. It issuperior to mechanical dust separation. In any case, when a relativelylarge mass of gas possesses correspondingly small dust content, the

forces to be produced for the dust separation with mechanical means mustbe produced through effect on the mass of gas, somewhat throughacceleration.

Electrofilters with non-homogeneous electric field are likewise knownper se. In breathing masks for this purpose frequently plate electrodesare provided, between which a mass of fibers for the different materialscoming into question, is packed in. These fibers bring about thenon-homogeneousness of the field and additionally a mechanicalseparation of the dust. On the other hand, the non-homogeneousness ofthe electric field thus attainable and therewith the degree ofeffectiveness of the electric separation of the dust are low.Unfavorable are the side effects of such filters deriving from the fiberpacking, among them above all the relatively great breathing resistanceand the low sound permeability of the filter. This has a particularlydisadvantageous effect in hot and non-supervisable operations.

Additionally, in the separation of the dust, the difficulty may arisethat masses of dust are of different polarity, causing a sudden electricdischarge. Under certain circumstances, mixtures capable of ignition,such as a pocket of natural gas, may be ignited.

SUMMARY OF THE INVENTION The invention proposes to eliminate suchdisadvantages, and to provide a filter, particularly a breathing filterfor dust filtering masks, in which for the non-homogenization of theelectric field, no fibers or fibrous materials are employed.

In accordance with the invention, this problem is solved by constructingeach electrode of metal wires with insulated surface, the metal wireshaving a diameter of approximately 0.1 mm. and the spacing of the metalwires of difi'erent polarity amounting to approxi- In the filtersaccording to the invention, the filter I fibers previously used arereplaced by good electrically conducting, metallic, thin wires withinsulated surface. The electric voltage may amount to from 300 to 500volts. By a good surface insulation of the wires, hardly any electricalenergy is used, so that a source of voltage of very low yield andtherewith of small dimensions is utilizable.

Such filter makes use of the electric charges of the dust particles forthe filtration operation. It prevents, however simultaneously, anaccumulation of electric charges of an indication, because the polarityof the electrodes changes periodically. In view thereof, ignition of thedust or surrounding gas mixtures is prevented. The filter has arelatively large free surface and accordingly a very low breathingresistance, but also has a good sound permeability.

The surface of the metal wires may be provided with hills and valleysfor the reinforced non-homogenization of the electric field. Such hillsand valleys may be produced by roughening the wire surface. The metalwires are provided with an insulating coating which may consist ofvarnish or lacquer customarily used therefor. The insulation of themetal wires is prepared moisture-repellent, where the filter is to beutilized in moist gases or gases charged with moisture.

The details of the inventionwill be explained more fully in thefollowing on the basis of the figures of the drawing.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENTFIGS. 1 to l f show, for example two individual wires and the effectattained in the filter according to FIG. 2a, where the wires are shownin cross-section. Between the wires is located an electric field.

FIG. 1a presumes that the left wire is charged positively and the rightis charged negatively. The electric field resulting between the wires isindicated with field lines, which extend from left to right. The fieldis nonhomogeneous. The non-homogeneousness results by means of thecurved surface of the electrodes. The insulating coating 3 which thesurfaces of the electrodes 1 and 2 carry, prevents a flow of currentafter application of an electric voltage even then when electricallyconducting particles of dust are separated in the filter so thateventually conducting bridges result between the wires.

The dust particles 4 are accumulated with negative charging 4 and withpositive charging on the insulated wire surfaces. The accumulatedparticles of dust change simultaneously the field between the wires,because the negative particles of dust accumulated on the wire 1 withpositive polarity and the dust particles 5 with positive charging on thewire 2 diminish the field with increasing dust separation. This completeremoval of the electric field between the electrodes 1 and 2 is to beprevented in the practice, and is illustrated in FIG. 1b.

In FIG. 1c is illustrated a condition which sets in when the voltage onhand before the dust separation is disconnected and this part of thecharging of the wires 1 and 2 is removed. Then there are still activesolely the charges of the dust particles, which build up a field whichis illustrated in dotted lines. When this field has the same strength asthe starting field according to FIG. la, then its direction is solelyreversed.

If now the polarity of the electrodes is reversed, that is the electricvoltage is reversed as to polarity, then there results the conditionaccording to FIG. 1d. The wire 1 is then negative, the wire 2 is chargedpositively. The charging of the dust particles and the source of voltageapplied accumulate. Subsequently, there results a field which isstronger than the starting field. In any case, the field weakens againwith the application of further particles of dust, this beingillustrated in FIG. 1e. FIG. 1 f shows the condition which fundamentallycorresponds to that according to FIG. 1b, in which the particles of dustdivided off on the surface of the wire exactly compensate with theircharges the field applied.

The filter illustrated in FIGS. 2 and 2a utilize several individualelements. Each element consists of a frame 6, on which are wound twolayers of wire 7 and 8. The wires of one layer are positive, those ofthe other layer are charged negatively. Negatively charged wires areillustrated solely in their circular contour, positively charged wiresare illustrated by means of filled out circles. The wires which form theelectrodes do not need to lie parallel to one another, that is, to bearranged like a harp, but rather, net-like arrangements are alsoutilizable.

The frames 6 are layered superimposed in the filter and are held spacedfrom one another by elements 9. In i the embodiment by way of example,eight individual frames are present.

In the illustrated filter, the period of time between two polaritychanges is greater than the duration of the dust particles in thefilter. It is, however, smaller than the time required for theneutralization of the electrodes through dust charges. In practice,period changes result between several seconds to several minutes.

Although the invention has been explained mainly for breathing filtersfor dust-filtering masks, among them chiefly for such as used in mining,the outstanding characteristics of such filters may be utilized also inother branches of industry, and filters with other dimensions may becarried out, whereby the resistance to temperature of such filters,which reaches beyond several C., still substantially increases theirpossibilities of use.

What I claim is:

1. Breathing filter especially for dust masks, for the separation ofdust particles from gases comprising a plurali of frames arranged insupe osed relation, positive y and negatively charged e ec rodes on eachframe, said electrodes comprising two similar layers of metal wiresextending back and forth between the sides of each frame, the wires ofone layer being charged positively and those wires of the other layerbeing negatively charged, a moisture-repellent insulating coating foreach of said wires, each wire being of a diameter of approximately 0.1mm. and wires of different polarity being spaced approximately 0.5 mm.,hills and valleys on the surface of saidwires for the reinforcednonhomogenization of the electric field, and spacers separating oneframe from another, whereby the polarity of the electrodes may bechanged in periods which are greater than the duration of the dustparticles in the filter but less than the time required for theequalization of the potential difference of the electrodes.

2. Breathing filter according to claim 1, in which the wire layers areharp-like in arrangement.

1. Breathing filter especially for dust masks, for the separation ofdust particles from gases comprising a plurality of frames arranged insuperposed relation, positively and negatively charged electrodes oneach frame, said electrodes comprising two similar layers of metal wiresextending back and forth between the sides of each frame, the wires ofone layer being charged positively and those wires of the other layerbeing negatively charged, a moisture-repellent insulating coating foreach of said wires, each wire being of a diameter of approximately 0.1mm. and wires of different polarity being spaced approximately 0.5 mm.,hills and valleys on the surface of said wires for the reinforcednon-homogenization of the electric field, and spacers separating oneframe from another, whereby the polarity of the electrodes may bechanged in periods which are greater than the duration of the dustparticles in the filter but less than the time rEquired for theequalization of the potential difference of the electrodes.
 2. Breathingfilter according to claim 1, in which the wire layers are harp-like inarrangement.